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Jul 10, 2023

SPR Machine Discovers New Productivity in Brass

Three partners contributed their diverse manufacturing and machining

Three partners contributed their diverse manufacturing and machining experience—and their last initials—to found SPR Machine in 2002. From 2,500 square feet, this Hamilton, Ohio, machine shop has grown to 78,000 square feet and a floor filled with 14 mills, along with lathes, welding and inspection equipment—all dedicated to producing high-quality work from 60" down to 0.0005" for customers predominantly in the aerospace and medical industries.

All that talent, experience and entrepreneurial energy make SPR Machine an open-minded shop that approaches new growth challenges with enthusiasm. When one of those challenges presented itself in the form of a part-material switch from steel to brass and a push to see how much cycle time SPR could save through high-speed machining, SPR jumped at the opportunity.

It wound up leading the shop to new equipment, insights, personnel qualifications – and a renewed respect for the versatility and machining performance of brass.

The opportunity started when co-founder Scott Pater, an off-road and radio-controlled car enthusiast, combined those passions to race off-road RC cars with a friend.

When that friend created a reengineered version of an RC part and began marketing it to hobby shops, Pater showed him that SPR would make a better supplier than a vendor in China, especially given that off-shore ordering meant waiting months for parts.

The initial design specified 12L14 steel, which corroded and swelled, making it difficult to remove the part once it was in use.

Aluminum solved the corrosion problem but lacked the strength and weight for stability in a small vehicle with a low center of gravity.

Brass offered both, along with the good looks to make the part attractive to customers and reinforce SPR's quality-centric approach. Additionally, brass didn't produce the long, stringy bird's-nest chips SPR experienced with other metals, especially in a part with a nearly four-inch-long drilled-through hole.

"Brass is quicker to machine, with chips that flow smoothly out of the machine, and customers like what they see in the finished parts," Pater said.

For this job, Pater invested in the company's second CNC lathe, a seven-axis Swiss-style Ganesh Cyclone GEN TURN 32-CS with dual 6,000-rpm spindles, 27 tools, linear ways and a 12-foot hydrostatic bar feeder.

"Initially, we were running this RC part on an SL10 lathe. We had to run one side, take out the part and flip it around to finish the back," Pater said. "On the Ganesh, the part is completely done when it comes out of the machine."With a new machine in house, SPR needed to find the right employee to dive into its learning curve.

David Burton, an operator who previously worked in SPR's deburring department, took on the challenge. In a few months, he learned block coding and G-code for a two-spindle machine and produced the initial program for the part.

SPR's involvement with Cincinnati-based TechSolve, a consulting firm that provides machinability evaluation testing services, led the shop to a unique opportunity to optimize this part in conjunction with the Copper Development Association (CDA), the non-profit trade group that represents producers and users of copper, bronze and brass.

In exchange for allowing TechSolve to guide SPR's production parameters, the shop would gain the ultimate optimization parameters from experts in the machine and the material.

Along with turning, the part initially required ball milling, drilling numerous deep holes and boring out a bearing surface in the inner diameter.

The Ganesh's multiple spindles and axes saved production time, but Burton's initial production program yielded a six-minute, 17-second part cycle, which translated to 76 units per eight-hour shift.

After SPR implemented TechSolve's recommendations, cycle time dropped to two minutes and 20 seconds, and parts per shift rose to 191.

To achieve this optimization, TechSolve identified several areas in which SPR could reduce cycle time.

Instead of ball milling, SPR could substitute broaching, ganging up parts and machining five slots at once—a strategy that most likely would have not worked in making the part from stainless steel or steel.

With a carbide drill for pecking, more-aggressive feeds and depths, and fewer retracts, along with an increased depth of cut for roughing, SPR saved still more time. Balancing the workload between the two spindles meant that neither waited for the other to complete a process, which increased throughput.

Finally, the sheer machinability of brass meant that the process could proceed at high speeds and feeds by definition.

SPR allowed TechSolve to optimize the process so the shop could see the gains it could make with brass on other production parts.

Burton's initial production program represented a starting point, and SPR's own optimizations reduced cycle times further.

But the ability to see the full process from analysis through production optimization represented a unique opportunity, as did the use of brass itself.

Brass offered numerous advantages, as SPR realized, and among them, several stood out on this project in particular.

With high-speed machining, brass made quick work of drilling deep holes, holding accuracy and extending tool life throughout long shifts.

Brass also made deburring much easier than in stainless steel or steel machined at high speeds.

Because brass requires less machining force than steel, machine wear was reduced as well, with higher speeds producing less deflection. And because brass scrap holds up to 90% of its value, SPR was able to cash in machining chips through recycling programs.

As Pater put it, "Brass offers a large productivity upside. Your equipment is your limiting factor unless you have an advanced tool that can actually handle high-speed machining. By upgrading your machine tools, you can tap into the real potential of brass."

SPR's lathe department turns more brass than anything else, although the shop as a whole also deals with aluminums, stainless steels and exotic materials, including plastics such as PEEK. Like many of the jobs SPR designs, engineers and produces, its brass parts play crucial roles in space exploration, military telemetry, medical tools and other applications that often involve non-disclosure agreements for a who's-who list of customers, many of whom SPR is not permitted to name as a result. The types of work the shop takes on mean that tolerances divide SPR's workflow, with roughly half at ± three thousandths and the remainder at ± three tenths.

SPR welcomed CDA's and TechSolve's input, and the benefits were mutual.

CDA's director of rod and bar, Adam Estelle, noted that "High-speed machining with brass helps shops justify the investment in new equipment because of the increased revenue and productivity it generates and the new business it makes possible. We are thrilled with the results SPR achieved which should inspire other shops to be more aggressive with brass."

Senior TechSolve engineer George Adinamis complimented SPR for its openness, saying that "SPR shared information and trusted us, which was a big compliment, and the entire process was a total collaboration."

In fact, some of SPR's customers rely on Scott Pater's input into part development, part designs and material recommendations, so SPR could make a case for brass on other projects and see its customers adopt its advice.

The future looks bright for SPR Machine.

Along with the parts it designs and creates for other customers, it has become a supplier itself, creating a tombstone workholding fixture that enables four-axis lathes and mills to work with round and flat bar stock and castings.

"Our design offers us more throughput, and it's lighter weight but still very rigid, so a single person can put it on a machine," Pater said.

SPR's complex background contributes to its innovative approach to projects, collaboration and success—and brass plays a growing role in its workflow.

With this collaborative experience to highlight the advantages of working with brass, SPR Machine will be on the lookout for other opportunities to transition parts for heightened efficiency and profitability.

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